ASTM B796-07
(Test Method)Standard Test Method for Nonmetallic Inclusion Content of Powders Intended for Powder Forging (PF) Applications
Standard Test Method for Nonmetallic Inclusion Content of Powders Intended for Powder Forging (PF) Applications
SIGNIFICANCE AND USE
The extensive porosity present in pressed and sintered ferrous materials masks the effect of inclusions on mechanical properties. In contrast, the properties of material powder forged to near full density are strongly influenced by the composition, size, size distribution, and location of nonmetallic inclusions.
The test for nonmetallic inclusions in powder forged steels is useful as the following:
Characteristic to classify or differentiate one grade of powder from another.
Means of quality comparison of powders intended for powder forging, lot to lot.
Significant variations in nonmetallic inclusion content will occur if:
The powder used to form the test specimen does not meet powder forging quality standards for nonmetallic inclusion content.
Processing of the powder forged test specimen has been carried out under conditions that do not permit oxide reduction or allow oxidation of the test specimen, or both.
SCOPE
1.1 This test method covers a metallographic method for determining the nonmetallic inclusion level of powders intended for powder forging (PF) applications.
1.2 The test method covers repress powder forged test specimens in which there has been minimal lateral material flow ( 1%). The core region of the powder forged test specimen shall contain no porosity detectable at 100.
1.3 This test method is not suitable for determining the nonmetallic inclusion level of powder forged test specimens that have been forged such that the core region contains porosity. At the magnification used for this test method residual porosity is hard to distinguish from oxide inclusions. Too much residual porosity makes a meaningful assessment of the inclusion population impossible.
1.4 The test method may be applied to materials that contain manganese sulfide (admixed or prealloyed) provided the near neighbor separation distance is changed from 30 m to 15 m.Note 1
The test method may be applied to powder forged parts where there has been a greater amount of material flow provided:
The near neighbor separation distance is changed, or
The inclusion sizes agreed between the parties are adjusted for the amount of material flow.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: B796 − 07
StandardTest Method for
Nonmetallic Inclusion Content of Powders Intended for
1
Powder Forging (PF) Applications
This standard is issued under the fixed designation B796; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* E768Guide for Preparing and Evaluating Specimens for
Automatic Inclusion Assessment of Steel
1.1 This test method covers a metallographic method for
determining the nonmetallic inclusion level of powders in-
3. Summary of Test Method
tended for powder forging (PF) applications.
3.1 A section representing the core region is cut from the
1.2 The test method covers repress powder forged test
powder forged test specimen and mounted for metallographic
specimens in which there has been minimal lateral material
grinding and polishing.
flow (<1%). The core region of the powder forged test
specimen shall contain no porosity detectable at 100×.
3.2 The polished sample is examined microscopically at a
magnification of 100× and a note made of inclusions larger
1.3 This test method is not suitable for determining the
than a predetermined size.
nonmetallic inclusion level of powder forged test specimens
that have been forged such that the core region contains
3.3 The maximum Feret’s diameter is used to determine
porosity.Atthemagnificationusedforthistestmethodresidual
inclusion size. A Feret’s diameter is a caliper diameter as
porosityishardtodistinguishfromoxideinclusions.Toomuch
illustrated in Fig. 1.
residual porosity makes a meaningful assessment of the inclu-
3.4 The fragmented nature of some inclusions means that
sion population impossible.
theirsizedeterminationissomewhatcomplicated.Theconcept
1.4 Thetestmethodmaybeappliedtomaterialsthatcontain
of near neighbor separation is used in determining inclusion
manganese sulfide (admixed or prealloyed) provided the near
size. If an inclusion is within a certain distance of its neigh-
neighbor separation distance is changed from 30 µm to 15 µm.
boring particles, it is considered a member of an inclusion
NOTE1—Thetestmethodmaybeappliedtopowderforgedpartswhere
cluster or agglomerate. Detected features within 30 µm of one
there has been a greater amount of material flow provided:
another are considered part of the same inclusion.The concept
The near neighbor separation distance is changed, or
The inclusion sizes agreed between the parties are adjusted for the
is illustrated schematically in Fig. 2.
amount of material flow.
3.5 The nonmetallic inclusion level of the test specimen is
1.5 This standard does not purport to address all of the
2
reported as the number of inclusions per 100 mm greater than
safety concerns, if any, associated with its use. It is the
or equal to the predetermined size.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
4. Significance and Use
bility of regulatory limitations prior to use.
4.1 The extensive porosity present in pressed and sintered
2. Referenced Documents
ferrous materials masks the effect of inclusions on mechanical
2
properties.Incontrast,thepropertiesofmaterialpowderforged
2.1 ASTM Standards:
to near full density are strongly influenced by the composition,
E3Guide for Preparation of Metallographic Specimens
size, size distribution, and location of nonmetallic inclusions.
4.2 The test for nonmetallic inclusions in powder forged
1
This test method is under the jurisdiction of ASTM Committee B09 on Metal
steels is useful as the following:
Powders and Metal Powder Productsand is the direct responsibility of Subcommit-
4.2.1 Characteristic to classify or differentiate one grade of
tee B09.11 on Near Full Density Powder Metallurgy Materials.
Current edition approved Oct. 1, 2007. Published November 2007. Originally
powder from another.
approved in 1988. Last previous edition approved in 2002 as B796–02. DOI:
4.2.2 Means of quality comparison of powders intended for
10.1520/B0796-07.
2
powder forging, lot to lot.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
4.3 Significant variations in nonmetallic inclusion content
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. will occur if:
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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B796 − 07
6.3 Transfer the heated cylindrical compact to a
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation:B796–02 Designation: B 796 – 07
Standard Test Method for
Nonmetallic Inclusion Content of Powders Intended for
1
Powder Forging (P/F)(PF) Applications
This standard is issued under the fixed designation B 796; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1This test method covers a metallographic method for determining the nonmetallic inclusion level of powders intended for
powder forging (P/F) applications. *
1.1 This test method covers a metallographic method for determining the nonmetallic inclusion level of powders intended for
powder forging (PF) applications.
1.2 The test method covers repress powder forged test specimens in which there has been minimal lateral material flow (< 1%).
The core region of the powder forged test specimen shall contain no porosity detectable at 1003.
1.3 This test method is not suitable for determining the nonmetallic inclusion level of powder forged test specimens that have
been forged such that the core region contains porosity.At the magnification used for this test method residual porosity is hard to
distinguish from oxide inclusions. Too much residual porosity makes a meaningful assessment of the inclusion population
impossible.
1.4 The test method may be applied to materials that contain manganese sulfide (admixed or prealloyed) provided the near
neighbor separation distance is changed from 30 µm to 15 µm.
NOTE 1—The test method may be applied to powder forged parts where there has been a greater amount of material flow provided:
The near neighbor separation distance is changed, or
The inclusion sizes agreed between the parties are adjusted for the amount of material flow.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2
2.1 ASTM Standards:
E 3Practice Guide for Preparation of Metallographic Specimens
E 768 Guide for Preparing and Evaluating Specimens for Automatic Inclusion Assessment of Steel
3. Summary of Test Method
3.1 Asection representing the core region is cut from the powder forged test specimen and mounted for metallographic grinding
and polishing.
3.2 The polished sample is examined microscopically at a magnification of 1003 and a note made of inclusions larger than a
predetermined size.
3.3 The maximum Feret’s diameter is used to determine inclusion size. A Feret’s diameter is a caliper diameter as illustrated
in Fig. 1.
3.4 Thefragmentednatureofsomeinclusionsmeansthattheirsizedeterminationissomewhatcomplicated.Theconceptofnear
neighbor separation is used in determining inclusion size. If an inclusion is within a certain distance of its neighboring particles,
it is considered a member of an inclusion cluster or agglomerate. Detected features within 30 µm of one another are considered
part of the same inclusion. The concept is illustrated schematically in Fig. 2.
2
3.5 The nonmetallic inclusion level of the test specimen is reported as the number of inclusions per 100 mm greater than or
equal to the predetermined size.
1
ThistestmethodisunderthejurisdictionofASTMCommitteeB09onMetalPowdersandMetalPowderProductsandisthedirectresponsibilityofSubcommitteeB09.11
on Near Full Density Powder Metallurgy Parts.Materials.
Current edition approved April 10, 2002.Oct. 1, 2007. Published May 2002.November 2007. Originally published as B–88.approved in 1988. Last previous edition
B–00.approved in 2002 as B 796 – 02.
2
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at service@astm.org. For Annual Book ofASTM Standards
, Vol 03.01.volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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B796–07
FIG. 1 Schematic illustration of Feret’s diameter.
FIG. 2 Schematic illustration of the “near neighbor” concept and
maximum Feret’s diameter.
4. Significance and Use
4.1 The extensive porosity present in
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